1. Field of Invention
The present invention relates to a personal computer system, especially to a terminating circuit module for automatic detection and a computer system that can automatically detect the terminating circuit module on the memory module slots.
2. Description of Related Art
A standard PC consists of a mainboard, interface card, and peripheral equipment, in which the mainboard is the heart of the computer system. On the mainboard, additional to the CPU, chip set, and slots for interface cards, a plurality of memory module slots for memory modules can also be provided. The number of memory module slots is varied as desired. A memory module set includes a plurality of memory members.
In the memory used in PC""s, such as synchronous dynamic random access memory (SDRAM), the access operation of the information is controlled by properly responding to a rising edge the clock signal in the system. Further, there is a double data rate DRAM (DDR DRAM), in which the memory is operated in the double data rate mode. The information access operation is controlled by the rising edge and the falling edge of the clock signal in the system to increase the speed of the memory.
The differences between SDRAM and DDR DRAM is described as following: (1) a normal clock signal is used in SDRAM and a differential clock signal is used in DDR DRAM; (2) VDD for SDRAM is equal to 3.3 V, and VDD for DDR DRAM is equal to 2.5 V, where VDDQ is also set to 2.5 V; (3) a reference is needed for SDRAM, but it is not needed for DDR DRAM, and the reference voltage thereof is xc2xd of VDDQ; (4) the information bus connected to SDRAM is a standard CMOS logic, and the information bus connected to DDR DRAM is a series stub terminated logic 2 (SSTLxe2x80x942); (5) a terminating voltage (VTT) is not needed for the SDRAM, and a VTT terminating voltage is needed for the information bus connected to DDR DRAM to absorb the reflected electric wave; (6) a pull-up resistor (or called a terminating resistor) is not needed for the information bus connected to SDRAM, but it is needed for the information bus connected to DDR DRAM. DDR DRAM has a greater advantage over SDRAM because of its double data rate.
Some chip sets in the commercially available mainboards support both SDRAM DRAM and DDR DRAM. However, only one memory module, such as SDRAM memory module or DDR DRAM memory module, can be used in the mainboard fabrication . This is because the information bus connected to DDR DRAM is a series stub terminated logic 2 (SSTLxe2x80x942). Therefore, a voltage regulator for VTT terminating voltage and a plurality of pull-up resistors are needed to be provided on the mainboard for DDR DRAM to absorb the reflected electric wave. Only one process for fabrication can be chosen, even if the chip set can support the SDRAM/DDR DRAM memory modules. For example, a mainboard supporting SDRAM and a mainboard supporting DDR DRAM can not be used together. Accordingly, the performance of the chip set can not be exhibited totally. When the mainboard supporting DDR DRAM is fabricated, components such as a voltage regulator and a plurality of pull-up resistors need to be provided on the mainboard. The used area of the printed circuit board (PCB) in the mainboard thus increases, resulting in increase of cost for the mainboard.
The present invention provides a terminating circuit module used in a computer system, in which a voltage regulator and a plurality of pull-up resistors can be provided on the terminating circuit module by the mainboard producer to reduce the area of the printed circuit board of the mainboard. Also, a nonvolatile memory can be provided on the terminating circuit module to store the information related to the terminating circuit module. The computer can automatically read the configuration of the memory and the terminated circuit module to prevent users from using the terminating circuit module in an incorrect way. A computer system, in which the SDRAM or DDR DRAM memory module can alternatively be used, can be further produced by the computer producer.
The present invention provides a terminating circuit module that can be applied on the mainboard of the computer system. The mainboard has a plurality of memory module slots each having a plurality of signal lines. The terminating circuit module comprises a printed circuit board which can be put into one of the memory module slots to electrically connect the terminating circuit module to the memory module slots. A voltage regulator is provided on the above printed circuit board to provide a terminating voltage. A plurality of terminating resistors are coupled to the voltage regulator, which are also provided on the printed circuit board. nonvolatile memory provided on the printed circuit board. Each of these terminating resistors has one end connected to the above signal lines and the other end connected to the above terminating voltage. When such terminating module is put into one of the memory module slots, the mainboard receives the configuration information of such terminating circuit module thereon by reading the information in the nonvolatile memory.
According to one of the preferred embodiments of the present invention, the information in the above nonvolatile memory corresponds to the specification of SPD, and the hardware thereof is associated with EEPROM. The memory module slots are the memory module slots satisfying the specification of JEDEC standard 184 pins. These memory module slots further include reference voltage pins, in which such reference voltage satisfies the standard of SSTL_2 bus in JEDEC specification.
According to one of the preferred embodiments of the present invention, the configuration information of the memory in the computer system, such as the slotted positions of the terminating circuit module and the memory, can be detected automatically by using the computer system according to the present invention to prevent users from using the terminating circuit module in an incorrect way.